This invention relates to a multistation switch system and is applicable to general industrial machines including, for example, an automatic assembling mahcine for print circuit boards or the like, packing machine, bottle making machine, tin making machine and press.
There is a systematized mass production system for producing products in plural production lines in parallel, transferring finished products to a common line in synchronization with one another and palletizing the finished products transferred to the common line. An example of layout of such mass production system is shown in FIG. 2. Individual production lines are designated by reference characters #1 through #n and these production lines will hereinafter be referred to as "stations". In other words, each of the stations #1-#n is an automatized production line which individually produces the products automatically. Arrows X indicate the direction in which semi-finished products are conveyed in the respective stations. Along conveying lines of the respective stations #1-#n are provided actuators or robots (hereinafter referred generally to as "actuators") A1-An at predetermined locations for performing an automatic work.
At the end of the respective stations #1-#n are provided transferring actuators B for transferring the products to a conveyor CVY. An arrow Y indicates the direction in which the products are conveyed on the conveyor CVY. At the end of the conveyor CVY is provided, if necessary, an actuator C for examining quality of the products or other purpose. At the end of the conveyor CVY is also provided a palletizing device PLT. The palletizing device PLT is operated in response to an operation of an actuator D to arrange the products which have been transferred from the conveyor CVY on a pallet P and thereby store these products.
A master device is provided for distributing and supplying materials or parts to the respective stations #1-#n. This master device has a main shaft MS which is driven by an unillustrated motor or like driving means. As this main shaft MS is rotated, materials and parts are distributed and supplied to the respective stations #1-#n. The respective stations #1-#n function as a kind of slave device with respect to the master device. That is, the respective stations #1-#n start their operation and perform various operations in synchronism with the operation of the master device. The operation for conveying semi-finished products in the respective stations #1-#n also is controlled in interlocked relation with the rotation of the main shaft MS. For example, the operation for conveying semi-finished products in the respective stations #1-#n may be performed in mechanically interlocked relation with the rotation of the main shaft MS or, alternatively, the operation for conveying semi-finished products may be performed in interlocked relation with the rotation of the main shaft MS by controlling conveying of the semi-finished products in the respective stations #1-#n in accordance with detected data of the rotational position of the main shaft MS. The conveyor CVY may be driven by independently controlling its running velocity or by controlling the running velocity in interlocked relation with the rotation of the main shaft MS. As the actuators A1-An, B, C and D, those adapted to works in respective processes such as solenoids, cylinders, motors, injectors and blowers are employed.
Take, for example, a process for manufacturing glass bottles. Material is distributed to respective stations #1-#n in interlocked relation with the rotation of the main shaft MS and a series of bottle manufacturing processes including insertion of the material to a rough mold, forming of a bottle by blowing or pressing in the rough mold, finish forming by blowing, annealing and printing are performed in the respective stations #1-#n in parallel with one another. In such production system, the operations of the actuators A1-An, B, C and D of the respective stations #1-#n are respectively controlled at predetermined timing in synchronism with the rotation of the main shaft MS. In the prior art system, a number of cam switches are provided on the main shaft MS for effecting such synchronized control and the operations of the actuators are controlled by outputs of these cam switches. Since, in this system, the operations of the stations #1-#n must be controlled independently from one another, the cam switches corresponding to the respective actuators A1-An, B, C and D must be provided for each of the stations #1-#n.
A mechanical type cam switch is disadvantageous in that change in the operation position of the switch is difficult, that there arises mulfunction in mechanical contact of the switch and that the system becomes complicated and bulky if a large number of mechanical type switched are provided. For eliminating these problems, Japanese Preliminary Patent Publication No. 58-222306 proposes a programmable cam system in which relation between a rotational position sensor for detecting the rotational position of a shaft and a desired switch on/off position is previously programmed and a programmed switch on/off signal is generated in accordance with the rotational position detected by the rotational position sensor. The disadvantages of the conventional mechanical type cam switches can be overcome by employing this programmable cam system.
In employing the above described programmable cam system in a production system having plural stations #1-#n as described above, however, a rotational position sensor and a cam switch data generation device must be provided independently for each station. Further, since works in the respective stations #1-#n must be performed in synchronization with one another at predetermined timing, a sequencer for controlling a cam output timing for each station must be provided above cam switch data generation devices for the respective stations. Particularly, when operations in the respective stations #1-#n are started and stopped at different times and in a predetermined order, a sequential control of timings for starting and stopping the operations in the respective stations is required. In a case where, for example, material is distributed sequentially to respective stations #1-#n in accordance with rotation of the main shaft MS and an operation is started sequentially in the order of the stations to which the material has been distributed, it is necessary to shift timings of starting and stopping the operation for the respective stations because otherwise there would arise inconvenience that actuators would be operated idly without material supplied thereto. Fo these reasons, the prior art programmable cam system requires a sequencer as a supervising device both in hardware and software aspects.
Accordingly, in the prior art system, an electronic type switch system such as the above described programmable cam system must be provided in a production system having plural stations which are independent work lines so that the system tends to become bulky and costly. Besides, the prior art system requires a sequencer as a supervising device controlling interrelation among respective stations so that the system tends to become bulky and costly also in this respect.